Torque Wrenches
The piston 32 and cylinder 30 of a torque wrench 18 are provided with pressurised fluid from a source 12 through an advance port 16, or from a pump 42 through a return port 38. The source 12 includes a large piston 26 driven from the pump 42 during the advance stroke, and a small piston 22 driving fluid to the advance port 46, or receiving fluid returned from the port 16, during the return stroke. Accordingly, the pistons 22 and 32 form a closed system for fluid moving between the cylinder 24 and the cylinder 30. The pistons 22, 26 are connected by a shaft 68 so that relatively low pressure applied to the piston 26 results in high pressure fluid delivered to the advance port 16. Consequently, a low pressure pump 42 can be used to provide high pressure drive via the source 12, or a low pressure return stroke via the return port 38.
The present invention relates to torque wrenches and in particular, to apparatus for supplying pressurised fluid for operation of powered torque wrenches.
In one aspect, embodiments of the invention provide apparatus comprising:
a source of pressurised fluid;
an outlet for supplying pressurised fluid from the source to a torque wrench to drive an action of the wrench;
wherein the source comprises a first piston and a first cylinder and the first piston is operable to deliver a predetermined volume of pressurised fluid for each action of the wrench, and wherein the first cylinder is operable to receive fluid returned from the torque wrench, between deliveries to provide, with the wrench, a closed system for the pressurised fluid.
The permitted stroke length of the first piston may be set to determine the predetermined quantity. Limit means may be provided to detect the first piston reaching a stroke limit. Limit means may be provided to detect the first piston reaching two stroke limits defining a stroke length. The first piston may have an advance stroke delivering fluid to the wrench, and a return stroke receiving fluid from the wrench.
The first piston may be mechanically coupled to a second piston in a second cylinder, to be driven by movement of the second piston. The hydraulic area of the second piston may differ from the hydraulic area of the first piston, whereby the first piston, in use, delivers fluid at a pressure which differs from the pressure applied to the second piston.
The hydraulic area of the first piston may be smaller than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a higher pressure than the pressure applied to the second piston.
Alternatively, the hydraulic area of the first piston may be larger than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a lower pressure than the pressure applied to the second piston.
The apparatus may further comprise a second source of pressurised fluid, operable to drive the second piston. The second source may be selectively operable to drive the second piston or to provide fluid to the torque wrench, whereby the sources create an advance action and a return stroke of the torque wrench.
The first source may supply pressurised fluid to an advance port of the wrench to drive an advance action of the wrench. The second source may supply pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
Alternatively, the first source may supply pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench. The second source may supply pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
In another aspect, embodiments of the invention provide apparatus comprising:
a first source of pressurised fluid;
an outlet for supplying pressurised fluid from the source to a torque wrench to drive an action of the wrench;
wherein the first source comprises a first piston in a first cylinder and mechanically coupled to a second piston in a second cylinder to be driven by movement of the second piston, the hydraulic areas of the first and second pistons being different, whereby the first piston, in use, delivers fluid at a pressure which differs from the pressure applied to the second piston.
The hydraulic area of the first piston may be smaller than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a higher pressure than the pressure applied to the second piston.
Alternatively, the hydraulic area of the first piston may be larger than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a lower pressure than the pressure applied to the second piston.
There may be a second source of pressurised fluid, operable to drive the second piston. The second source may be selectively operable to drive the second piston or to provide fluid to the torque wrench, whereby the sources create an advance action and a return stroke of the torque wrench.
The first source may supply pressurised fluid to an advance port of the wrench to drive an advance action of the wrench. The second source may supply pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
Alternatively, the first source may supply pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench. The second source may supply pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
The source may be operable to deliver pressurised fluid until a predetermined quantity has been delivered and thereafter to stop delivering until a subsequent action is required. The source may be operable to receive fluid returned from a torque wrench, between deliveries. The source may provide, with the wrench, a closed system for the pressurised fluid.
The first piston may have a permitted stroke length set to determine the predetermined quantity. Limit means may be provided to detect the first piston reaching a stroke limit. Limit means may be provided to detect the first piston reaching two stroke limits defining a stroke length. The first piston may have an advance stroke delivering fluid to the wrench, and a return stroke receiving fluid from the wrench.
Examples of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which:
In the example to be described, the source 12 is operable to deliver pressurised fluid until a predetermined quantity has been delivered to the advance port 16. Thereafter, the source 12 stops delivery until a subsequent advance action is required. In this example, the source comprises a first piston 22 in a first cylinder 24. The first piston 22 is mechanically coupled to a second piston 26 in a second cylinder 28. Movement of the first piston 22 is driven by movement of the second piston 26. As will be described more fully below, the hydraulic area of the second piston 26 is greater in this example than the hydraulic area of the first piston 22, whereby the first piston 22, in use, delivers fluid at a higher pressure than the pressure applied to the second piston 26.
In more detail, the wrench 18 has a hydraulic cylinder 30 containing a double acting piston 32. The piston 32 is mechanically coupled (schematically indicated at 34) to the rod and socket member 20 of the wrench 18, so that movement of the piston 32 causes the member 20 to turn, either in a first direction representing an advance stroke which tightens the threaded member 21 held by the wrench, or a return stroke. The coupling 34 incorporates a ratchet arrangement 36. Accordingly, each advance stroke further tightens the threaded member 21 and therefore requires relatively high torque. Each return stroke requires relatively little torque, sufficient to move the coupling 34 past the ratchet 36.
The advance port 16 supplies the wrench cylinder 30 on one face of the piston 32 allowing pressurised fluid supplied through the port 16 to drive an advance action of the wrench 18. The other side of the piston 32 is supplied through a return port 38 to drive the piston 32 in the opposite direction, to provide a return action.
The first and second pistons and cylinders, 22, 24, 26, 28 form an intensifier unit 40 supplied with hydraulic fluid from a pump 42 at low pressure (typically 250 bar, in one example). The pump 42 is driven by a motor 44, which may be driven electrically, pneumatically or by a petrol, diesel or gas internal combustion engine. The low pressure output of the pump 42 can be applied selectively to the intensifier unit 40 or to the return port 38. A valve 46 controls the connections between the pump 42 and the intensifier unit 40 and return port 38, and also connections to a reservoir 48. The valve 46 is a two position, four way valve indicated schematically in
In the alternative position of the valve 46, the ports 50, 58 are reversed with respect to the ports 52, 56, so that the low pressure supply from the pump 42 is supplied to the return port 38, and the port 54 of the second cylinder 28 is connected through to the reservoir 48.
The valve 46 is a solenoid operated valve in this example, having a solenoid 60 controlled from a control unit 62.
The example intensifier unit 40, illustrated simply in
The second piston 26 moves in the second cylinder 28, having appropriate seal rings 64 to provide a chamber 66 between the second piston 26 and the port 54. The piston 26 carries an axial shaft 68 on which the first piston 22 is formed to be movable in the first cylinder 24. Seal rings 70 are provided to form a sealed chamber 72 between the first piston 22 and the outlet 14. The cylinders 24, 28 are secured together at 74, for example by bolts or other fastenings.
The second piston 26 carries a control rod 76 parallel to the shaft 68, which passes out from the cylinders 24, 28 to extend alongside the cylinder 24, to move to and fro with the pistons 22, 26. Two sensors 78 are mounted alongside the cylinder 24 and are, in this example, electrical switches, micro switches, Hall effect devices or similar sensors. In use, when the pistons 22, 26 move to the right (as illustrated in
Outputs from the sensors 78 are applied to the control unit 62, at 80 (
Thus, for an advance stroke, the pump 42 supplies the port 54 driving the second piston 26 to the right (
In this example, a predetermined volume of pressurised fluid is delivered to the advance port 16, for each advance stroke, until the sensor 78a is triggered to end the advance stroke. The fluid is then returned to the first cylinder 24, on the return stroke. Delivering a predetermined volume of fluid on each advance stroke results in the length of each advance stroke of the wrench being the same.
During the advance stroke, the intensifier unit 40 receives low pressure hydraulic fluid through the port 54 and delivers hydraulic fluid through the outlet port 14. It is readily apparent from
Accordingly, the intensifier unit 40 results in delivery of relatively high pressure fluid to the advance port 16, but powered by the low pressure pump 42. This provides the necessary pressure to drive an advance stroke. For a return stroke, the low pressure delivered by the pump 42 is adequate and is thus applied directly to the return port 38, resulting in the wrench 18 executing a return action. Accordingly, both actions of the wrench 18 are driven by a single pump 42 which delivers low pressure fluid.
It may be desirable to incorporate pressure relief valves (illustrated in
In the unit 40a, the pistons 22a, 26a are provided by opposite faces of the same piston element 84. Thus, they are directly connected together as faces of the element 84. A shaft 86 extends from the piston 22a, thus reducing its hydraulic area below that of the second piston 26a. The cylinders 24a, 28a are concentric extensions of each other and are closed at one end by a cap 88, through which the shaft 86 extends and through which the outlet port 14a communicates with the chamber 72a. Beyond the cap 88, sensors 78aa, 78ba are mounted on a bar 90. The sensors 78aa, 78ba sense the passing of the tip of the shaft 86, in a manner similar to the tip of the rod 76 being sensed in the arrangement of
The arrangements described above have referred to a single hydraulic wrench 18 being supplied, but the arrangement can be used to supply multiple wrenches, if the volume delivered by a stroke of the piston 22, 22a is equal to or greater than the volume required to operate the sum of the wrenches being supplied.
In use, the pistons 22, 26 will repeatedly cycle to deliver relatively high pressure fluid to drive an advance action until the stroke limit is reached, and will then return before commencing a further advance action. This will continue until the setting of the pressure relief valve 55 (preferably adjustable) is reached, indicating that the predetermined torque limit has been reached.
In some circumstances, it may be convenient to provide a by-pass line 92 around the intensifier unit 40, 40a, allowing relatively fast, low pressure operation of the wrench 18. High pressure delivery from the outlet 14, 14a may be used without the return drive provided by the port 38, if other arrangements are provided for the return action.
The previous examples use a single source of relatively low pressure pressurised fluid, with the intensifier unit 40 being used to deliver high pressure to drive the advance action. In an alternative example, a single source of relatively high pressure pressurised fluid is used, as follows.
The unit 40, described above as an intensifier unit, can be used to reduce pressure, for example by reversing the unit 40, so that the port 54 is used to deliver to the wrench 30, and the port 14 is used to receive fluid from the pump 42.
The examples described above allow a torque wrench to be controlled to provide a predetermined torque from a single source of pressurised fluid. The use of a closed, high pressure system between the unit 40 and the wrench 30 allows the apparatus to cycle automatically until the torque limit set by the valve 46 is reached.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
Claims
1. Apparatus comprising:
- a source of pressurised fluid;
- an outlet for supplying pressurised fluid from the source to a torque wrench to drive an action of the wrench;
- wherein the source comprises a first piston and a first cylinder and the first piston is operable to deliver a predetermined volume of pressurised fluid for each action of the wrench, and wherein the first cylinder is operable to receive fluid returned from the torque wrench, between deliveries to provide, with the wrench, a closed system for the pressurised fluid.
2. Apparatus according to claim 1, wherein the permitted stroke length of the first piston is set to determine the predetermined quantity.
3. Apparatus according to claim 1, wherein limit means are provided to detect the first piston reaching a stroke limit.
4. Apparatus according to claim 3, wherein limit means are provided to detect the first piston reaching two stroke limits defining a stroke length.
5. Apparatus according to claim 1, wherein the first piston has an advance stroke delivering fluid to the wrench, and a return stroke receiving fluid from the wrench.
6. Apparatus according to claim 1, wherein the first piston is mechanically coupled to a second piston in a second cylinder, to be driven by movement of the second piston.
7. Apparatus according to claim 6, wherein the hydraulic area of the second piston differs from the hydraulic area of the first piston, whereby the first piston, in use, delivers fluid at a pressure which differs from the pressure applied to the second piston.
8. Apparatus according to claim 7, wherein the hydraulic area of the first piston is smaller than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a higher pressure than the pressure applied to the second piston.
9. Apparatus according to claim 7, wherein the hydraulic area of the first piston is larger than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a lower pressure than the pressure applied to the second piston.
10. Apparatus according to claim 6, wherein the apparatus further comprises a second source of pressurised fluid, operable to drive the second piston.
11. Apparatus according to claim 10, wherein the second source is selectively operable to drive the second piston or to provide fluid to the torque wrench, whereby the sources create an advance action and a return stroke of the torque wrench.
12. Apparatus according to claim 6, wherein the first source supplies pressurised fluid to an advance port of the wrench to drive an advance action of the wrench.
13. Apparatus according to claim 6, wherein the second source supplies pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
14. Apparatus according to claim 6, wherein the first source supplies pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
15. Apparatus according to claim 6, wherein the second source supplies pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
16. Apparatus according to claim 14, wherein the second source supplies pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
17. Apparatus comprising:
- a first source of pressurised fluid;
- an outlet for supplying pressurised fluid from the source to a torque wrench to drive an action of the wrench;
- wherein the first source comprises a first piston in a first cylinder and mechanically coupled to a second piston in a second cylinder to be driven by movement of the second piston, the hydraulic areas of the first and second pistons being different, whereby the first piston, in use, delivers fluid at a pressure which differs from the pressure applied to the second piston.
18. Apparatus according to claim 17, wherein the hydraulic area of the first piston is smaller than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a higher pressure than the pressure applied to the second piston.
19. Apparatus according to claim 17, wherein the hydraulic area of the first piston is larger than the hydraulic area of the second piston, whereby the first piston, in use, delivers fluid at a lower pressure than the pressure applied to the second piston.
20. Apparatus according to claim 17, further comprising a second source of pressurised fluid, operable to drive the second piston.
21. Apparatus according to claim 20, wherein the second source is selectively operable to drive the second piston or to provide fluid to the torque wrench, whereby the sources create an advance action and a return stroke of the torque wrench.
22. Apparatus according to claim 20, wherein the first source supplies pressurised fluid to an advance port of the wrench to drive an advance action of the wrench.
23. Apparatus according to claim 20, wherein the second source supplies pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
24. Apparatus according to claim 20, wherein the first source supplies pressurised fluid to a return port of the wrench, to drive a return stroke of the wrench.
25. Apparatus according to claim 20, wherein the second source supplies pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
26. Apparatus according to claim 24, wherein the second source supplies pressurised fluid to an advance port of the wrench, to drive an advance action of the wrench.
27. Apparatus according to claim 17, wherein the source is operable to deliver pressurised fluid until a predetermined quantity has been delivered and thereafter to stop delivering until a subsequent action is required.
28. Apparatus according to claim 27, wherein the source is operable to receive fluid returned from a torque wrench, between deliveries.
29. Apparatus according to claim 27, wherein the source provides, with the wrench, a closed system for the pressurised fluid.
30. Apparatus according to claim 27, wherein the first piston has a permitted stroke length set to determine the predetermined quantity.
31. Apparatus according to claim 30, wherein limit means are provided to detect the first piston reaching a stroke limit.
32. Apparatus according to claim 30, wherein limit means are provided to detect the first piston reaching two stroke limits defining a stroke length.
33. Apparatus according to claim 30, wherein the first piston has an advance stroke delivering fluid to the wrench, and a return stroke receiving fluid from the wrench.
Type: Application
Filed: May 22, 2008
Publication Date: Nov 27, 2008
Inventor: Paul Anthony Anson (Staffordshire)
Application Number: 12/125,547
International Classification: B25B 23/14 (20060101); B25B 23/00 (20060101);